Display Device and Method of Manufacturing Thereof

ABSTRACT

A novel display device with higher reliability having a structure of blocking moisture and oxygen, which deteriorate the characteristics of the display device, from penetrating through a sealing region and a method of manufacturing thereof is provided. According to the present invention, a display device and a method of manufacturing the same comprising: a display portion formed by aligning a light-emitting element using an organic light-emitting material between a pair of substrate, wherein the display portion is formed on an insulating layer formed on any one of the substrates, the pair of substrates is bonded to each other with a sealing material formed over the insulating layer while surrounding a periphery of the display portion, at least one layer of the insulating layer is made of an organic resin material, the periphery has a first region and a second region, the insulating layer in the first region has an opening covered with a protective film, the sealing material is formed in contact with the opening and the protective film, an outer edge portion of the insulating layer in the second region is covered with the protective film or the sealing material.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a display device comprising an element(hereinafter referred to as a light-emitting element) in which alight-emitting material is interposed between a pair of electrode, andto a method of manufacturing thereof. More particularly, the presentinvention relates to a sealing structure of a display device using alight-emitting material that generates electroluminescence (EL) and amethod of manufacturing the same.

2. Description of the Related Art

In recent years, development of a display device (EL display device)using a light-emitting element (hereinafter referred to as an ELelement) which utilizes electroluminescent phenomenon of alight-emitting material has been advanced. Since the light-emittingelement of the EL display device is a self-luminous type, a backlight,which is used for a conventional liquid crystal display device, isunnecessary. In addition, the EL display device has merits of the wideviewing angle, the excellent visibility and the like.

It has been said that the EL element emits photons as follows. Byapplying a voltage to an organic compound layer interposed between apair of electrodes, electrons injected from a cathode and positive holesinjected from an anode recombine together at a center of luminescence inthe organic compound layer to form excited molecules, and hence, energyis released to emit photons when the excited molecules return to thebase state. There are known two different excited states: a singletexcited state and a triplet excited state. Luminescence can be generatedthrough either of the states.

Although there are inorganic light-emitting materials and organiclight-emitting materials as the material used for the EL element, theorganic light-emitting materials so which can be driven at lower voltagethan the inorganic light-emitting materials has been attracting muchattention.

However, when the EL element comprising an organic material is drivenfor a certain period, luminance and light emitting properties such asnonuniformity of light emission are drastically deteriorated as comparedwith those in the initial state, which results in a problem of lowreliability. The low reliability of the EL element is a limiting factorin practical application of the EL material.

Further, moisture and oxygen which penetrate from outside into the ELelement are another factor of deteriorating the reliability of the ELelement.

In an EL display device (panel) using an EL element, moisturepenetrating into the interior of the device causes a serious degradedreliability, which further reads to a dark spot, shrinkage, anddeterioration in luminance from a periphery of The EL display device.The dark spot is a phenomenon in which luminance is partly degraded(which includes nonluminous portion), and is generated when a hole isformed in an upper electrode. Meanwhile, the shrinkage is a phenomenonin which luminance is deteriorated from edges of a pixel.

Accordingly, a display device comprising a structure for preventing theabove-mentioned deteriorations of the EL element has been researched anddeveloped. In order to prevent the foregoing problems, there is a methodin which the EL element is accommodated in an airtight container and adesiccant is provided in an airtight space (for ample, see patentdocument 1).

[Patent Document 1]

Japanese Patent Application Laid-Open No. Hei 9-148066

Further, there is another method in which a sealing material is formedon an insulator with the EL element formed thereon, and an airtightspace surrounded by a covering material and the sealing material isfilled with a filler such as a resin so as to shield the EL element froman exterior portion (for example, see patent document 2).

[Patent Document 2] Japanese Patent Application Laid-Open No. 13-203076

FIG. 5 shows a top view of the EL display device as disclosed in thepatent document 2. Reference numeral 401 surrounded by a doted linedenotes a source side driving circuit, reference numeral 402 denotes agate side driving circuit, reference numeral 403 denotes a pixelportion, and reference numeral 409 denotes a flexible printed circuit(FPC). Further, reference numeral 404 denotes a covering material,reference numeral 405 denotes a first sealing material, and referencenumeral 406 denotes a second sealing material. FIG. 6 shows a crosssectional view of a conventional EL display device as illustrated inFIG. 5 (the second sealing material 406 is not illustrated therein). InFIG. 6, reference numeral 800 is a substrate, reference numeral 801 isan electrode, reference numeral 811 is a pixel electrode, referencenumeral 812 is an insulating film, reference numeral 813 is an EL layerreference numeral 814 is a cathode, and reference numeral 815 is an ELelement. As illustrated in FIG. 6, in a sealing region, the EL elementis encapsulated in an interior portion with the sealing material 817.

According to the patent documents 1 and 2, in the sealing region, the ELelement is protected from moisture exists outside by providing thesealing material as depicted in FIG. 6.

With respect to the patent document 1, however when the structure inwhich the EL element is accommodated in the airtight container is taken,the EL display device is grown in size for the size of the airtightcontainer. Although the EL display device is only grown in size, thelight-emitting area is not changed. Therefore, the advantage of a thinEL display device, which dispenses with a backlight cannot be utilized.

Furthermore, with respect to the patent document 2, since the sealingmaterial is applied to a substrate to form the airtight space in thesealing region, it is inevitable that the EL display device is grown insize.

As set forth above, as the area of the sealing region is increased,nonluminous regions are further increased. Accordingly, it is inevitablethat the display device is grown in size in order to obtain alight-emitting portion with a desired area.

In view of the above mentioned problems, a display device with a narrowframe in which the scaling region is made as narrow as possible has beenresearched and developed (for example, see patent document 3).

[Patent Document 3]

Japanese Patent Application Laid-Open No. 2002-329576

In the patent document 3, a sealing pattern used for sealing is formedover a substrate with a depression formed thereon. When the width of thesealing pattern in the sealing region is narrowed in order to achieve anarrower frame portion, since the surface area through which the sealingpattern and the substrate contact becomes large, reduction in the bondstrength therebetween can be suppressed.

However, in the patent document 3, the sealing material is applied overthe substrate in the sealing region as well as the patent documents 1and 2, and therefore there is a limitation on a narrower frameformation.

Further there is another method in which the sealing material isdirectly applied to a film such as an interlayer film, and a protectivefilm as substitute for the substrate so as to eliminate the sealingregion for applying the sealing material. An EL display devicemanufactured according to this method is illustrated in FIG. 7. Anenlarged cross sectional view of an edge of the sealing region takenalong a line C-C′ in FIG. 5 is illustrated in FIG. 14.

As depicted in FIG. 14, a first coating film 53, a second coating film54, a third coating film 55, and a fourth coating film 56 are laminatedover a substrate 50 in a display device. Further, a sealing material 52is applied thereon. This structure allows to reduce the sealing region.The first coating film 53, the second coating film 54, the third coatingfilm 55, and the fourth coating film 56 corresponds to a base film, agate insulating film, a protective film, an interlayer film, aconductive film, and the like, respectively.

However, when the sealing material for sealing is formed over alaminated film as illustrated in FIG. 14, each laminated film isdirectly in contact with an ambient air outside of the display device.Therefore, moisture and oxygen existing outside of the display devicepenetrate into the display device through the each laminated film. Inaddition, when a material having high moisture permeability such asacrylic is used as the interlayer film, more moisture and oxygenpenetrate into the display device.

Moisture and oxygen penetrate through the acrylic included in theinterlayer film or top and bottom interfaces of acrylic by using theacrylic as a path. The moisture and oxygen ultimately reach to the ELelement via a disconnection portion in a contact hole due to poor filmformation properties of source and drain electrodes and the like. Theinterior of the EL display device and the EL element are contaminated bythese moisture and oxygen, thereby causing various deteriorations suchas deterioration of the electric characteristics, a dark spot, andshrinkage.

SUMMARY OF TAB INVENTION

In view of the foregoing problems, it is an object of the presentinvention to provide an EL display device with higher reliability bypreventing intrusion of moisture and oxygen that reads to deteriorationin characteristics of an EL element, without increasing the size of thedevice, and to provide a method of manufacturing thereof.

In the present invention, a film having functions of blockingcontaminants from penetrating into the display device, protecting adisplay element, and preventing various deteriorations is referred to asa protective film.

A display device of the present invention comprises: a pair ofsubstrates; an insulating layer comprising an organic resin material,formed over one of the substrates; a display portion formed over theinsulating layer, the display portion comprising a light-emittingelement including an organic material; and a scaling materialsurrounding a periphery of the display portion, formed over theinsulating layer, wherein the pair of substrates is bonded to each otherwith the sealing material, wherein the periphery of the display portioncomprises a first region and a second region, wherein the insulatinglayer in the first region has an opening covered with a protective film,and the sealing material is formed in contact with the opening and theprotective film, and wherein an outer edge portion of the insulatinglayer in the second region is covered with the protective film or thesealing material.

A display device of the present invention comprises: an insulating layercomprising an organic resin material, formed over one of the substrates;a display portion formed over the insulating layer, the display portioncomprising a light-emitting element including an organic material; and asealing material surrounding a periphery of the display portion, formedover the insulating layer, wherein the pair of substrates is bonded toeach other with the sealing material, wherein the periphery of thedisplay portion comprises a first region and a second region, whereinthe insulating layer in the first region comprises a plurality ofdepressions and projections covered with a protective film, and thesealing material is formed in contact with the plurality of depressionsand projections and the protective film, and wherein an outer edgeportion of the insulating layer in the second region is covered with theprotective film or the sealing material.

A display device of the present invention comprises: first and secondsubstrates; an insulating layer comprising an organic resin material,formed over the first substrate; a display portion formed over theinsulating layer, the display portion comprising a light-emittingelement including an organic material; and a sealing materialsurrounding a periphery of the display portion, formed over theinsulating layer, wherein the first and second substrates are bonded toeach other with the sealing material, wherein the periphery of thedisplay portion comprises a first region and a second region, whereinthe insulating layer and the second substrate in the first region has aplurality of depressions and projections, the plurality of depressionsand projections of the insulating layer are covered with a protectivefilm, wherein in the first region, the scaling material is formed incontact with the plurality of depressions and projections covered withthe protective film and the plurality of depressions and projections ofthe second substrate, and wherein an outer edge portion of theinsulating layer in the second region is covered with the protectivefilm or the sealing material.

A display device of the present invention comprises: first and secondsubstrates; an insulating layer comprising an organic resin material,formed over the first substrate; a display portion formed over theinsulating layer, the display portion comprising a light-emittingelement including an organic material; and a sealing materialsurrounding a periphery of the display portion, formed over theinsulating layer, wherein the first and second substrates are bonded toeach other with the sealing material, wherein the periphery of thedisplay portion comprises a first region and a second region, whereinthe insulating layer and the second substrate comprises a plurality ofdepressions and projections covered with a protective film, wherein thesealing material in the first region is formed in contact with theinsulating layer the plurality of depressions and projections of thesecond substrate, and the protective film, and wherein an outer edgeportion of the insulating layer in the second region is covered with theprotective film or the sealing material.

The first substrate comprising the insulating layer and the secondsubstrate are adhered to each other so as to match the depressions withthe corresponding projection formed thereon respectively, and thereforethe sealing material sandwiched by these substrates is pressed andextended to a gap between the depressions and projections to bond thesubstrates. Accordingly, even if minute amounts of moisture and oxygenintrude from the sealing material, since the moisture and oxygen have tomove through a long zigzag path along the depressions and projections,they hardly penetrate into the interior of the display device. As aresult, the effect of blocking the contaminants can be further improved,thereby providing a display device having high reliability.

According to the above-mentioned structure, the outer edge portion ofthe insulating layer in the first region may be coated with theprotective film or the scaling material. In the case of covering theouter edge portion of the insulating layer, the insulating layer is notexposed to the atmospheric air, and hence, the effect of blocking thecontaminants is further enhanced. Note that the outer edge portion ofthe insulating layer may be coated with the scaling material. In suchcase, the outer edge portion is preferably covered with a scalingmaterial having a film thickness and width that do not damage the effectof narrower frame formation.

According to the above-mentioned structure, the protective film may bemade so of one kind or plural kinds of films selected from thinconductive films and thin insulating films. As for the thin conductivefilms, a film made of one kind or plural kinds of elements selected fromthe group consisting of Al, Ti, Mo, W, and Si may be employed.Meanwhile, as for the thin insulating films, a film made of one kind orplural kinds of materials selected from silicon nitride, silicon oxide,silicon oxynitride, aluminum nitride, aluminum oxynitride, aluminumnitride oxide, aluminum oxide, diamond like carbon (DLC), a carbonnitride film (CN), siloxane polymer may be used.

According to the above-mentioned structure, as for the organic resinmaterial, a film composed of one kind or plural kinds of materialsselected from acrylic, polyamide, polyimide, resist, benzocyclobutene,and siloxane polymer or laminated layer of these, etc. may be used. Thesiloxane polymer is a material in which a skeleton structure is composedby bonding silicon (Si) and oxygen (O), and a substituent comprises atleast one kind of hydrogen, fluorine, alkyl group, and aromatichydrocarbon. A film formed by applying siloxane polymer and then burningcan be referred to as a silicon oxide film (SiOx) containing alkylgroup.

A method of manufacturing a display device of the present inventioncomprises: forming an insulating layer comprising an organic resinmaterial over a first substrate; forming an opening in the insulatingfilm; forming a protective film on the opening; forming a displayportion comprising a light-emitting element including an organicmaterial over the insulating layer, forming a sealing materialsurrounding a periphery of the display portion, in contact with theopening and the protective film; and bonding the first substrate to asecond substrate with the sealing material, wherein the periphery has afirst region and a second region, wherein the opening is formed in theinsulating layer of the first region, and wherein an outer edge portionof the insulating layer in the second region is covered with theprotective film or the scaling material.

A method of manufacturing a display device of the present inventioncomprises: forming an insulating layer comprising an organic resinmaterial over a first substrate; forming a plurality of depressions andprojections in the insulating film; forming a protective film on theplurality of depressions and projections; forming a display portioncomprising a light-emitting element including an organic material overthe insulating layer forming a sealing material surrounding a peripheryof the display portion, in contact with the plurality of depressions andprojections and the protective film; and bonding the first substrate toa second substrate with the sealing material, wherein the periphery hasa first region and a second region, wherein the plurality of depressionsand projections are formed in the insulating layer of the first region,and wherein an outer edge portion of the insulating layer in the secondregion is covered with the protective film or the sealing material.

A method of manufacturing a display device of the present inventioncomprises: forming an insulating layer comprising an organic resinmaterial over a first substrate; forming a plurality of depressions andprojections in the insulating layer; covering the plurality ofdepressions and projections with a protective film; forming a displayportion comprising a light-emitting element including an organicmaterial over the insulating layer; forming a scaling materialsurrounding a periphery of the display portion over the insulatinglayer; and bonding the first substrate to a second substrate with thesealing material, wherein the periphery has a first region and a secondregion, wherein the plurality of depressions and projections formed inthe insulating layer is provided in the first region, wherein in thefirst region, the sealing material is formed in contact with theplurality of depressions and projections covered with the protectivefilm and a plurality of depressions and projections formed on the secondsubstrate, and wherein an outer edge portion of the insulating layer inthe second region is covered with the protective film or the sealingmaterial.

A method of manufacturing a display device of the present inventioncomprises: forming an insulating layer comprising an organic resinmaterial over a first substrate; forming a plurality of depressions andprojections on the insulating layer; covering the plurality ofdepressions and projections on the insulating layer with a protectivefilm; forming a display portion comprising a light-emitting elementincluding an organic material over the insulating layer; forming asealing material surrounding a periphery of the display portion over theinsulating layer; and bonding the first substrate to a second substratewith the sealing material, wherein a plurality of depressions andprojections are formed on the second substrate, and the plurality ofdepressions and projections on the second substrate is covered with aprotective film, wherein the periphery has a first region and a secondregion, wherein the plurality of depressions and projections on theinsulating layer is provided in the first region, wherein in the firstregion, the sealing material is in contact with the protective filmscovering the plurality of depressions and projections on the insulatinglayer and the second substrate, and wherein an outer edge portion of theinsulating layer in the second region is covered with the protectivefilm or the sealing material.

The first substrate comprising the insulating layer and the secondsubstrate are adhered to each other so as to fit the depressions intothe co responding projections formed thereon respectively, and thereforethe sealing material sandwiched by these substrates is pressed andextended to a gap between the depressions and projections to bond thesubstrates. Accordingly, even if minute amounts of moisture and oxygenintrude from the sealing material, since the moisture and oxygen have tomove through a long zigzag path along the depressions and projections,they hardly penetrate into the interior of the display device. As aresult, the effect of blocking the contaminants can be further improved,thereby providing a display device having high reliability.

According to the above-mentioned structure, the outer edge portion ofthe insulating layer located outside of the sealing material may becoated with the protective film. In the case of covering the outer edgeportion of the insulating layer, the insulating layer is not exposed tothe atmospheric air and hence, the effect of blocking the contaminantsis further enhanced. Note that the outer edge portion of the insulatinglayer may be coated with the sealing material. In such case, the outeredge portion is preferably covered with a sealing material having a filmthickness and width that do not damage the effect of narrower frameformation.

According to the above-mentioned structure, the protective film may bemade of one kind or plural kinds of films selected from thin conductivefilms and thin insulating films. As for the thin conductive films, afilm made of one kind or plural kinds of elements selected from thegroup consisting of Al, Ti, Mo, W, and Si may be employed. Meanwhile, asfor the thin insulating films, a film made of one kind or plural kindsof materials selected from silicon nitride, silicon oxide, siliconoxynitride, so aluminum nitride, aluminum oxynitride, aluminum nitrideoxide, aluminum oxide, diamond like carbon (DLC), a carbon nitride film(CN), siloxane polymer may be used.

According to the above-mentioned structure, as for the organic resinmaterial, a film composed of one kind or plural kinds of materialsselected from acrylic, polyamide, polyimide, resist, benzocyclobutene,and siloxane polymer, or laminated layer of these etc. may be used.

According to the present invention, the path for moisture in theinsulating layer which contains the organic resin material of thedisplay device is blocked. Therefore, it is possible to prevent moistureand oxygen exist outside of the display device from penetrating into adisplay element in the interior of the display device via the insulatingto film containing an organic material with a hygroscopic property andthe like. In addition, it is also possible to prevent variousdeteriorations caused by moisture and oxygen such as contamination ofthe interior of the display device, deterioration in the electriccharacteristics, a dark spot, and shrinkage, thereby enhancing thereliability of the display device. Since the film constituting thedisplay device is used as the protective film according to the presentinvention, the display device with high reliability can be manufacturedwithout increasing the number of steps.

By utilizing the structure of the present invention, followingadvantageous effects can be obtained.

According to the present invention, it is possible to prevent moistureand oxygen exist outside of a display device from penetrating into adisplay element in the interior of the display device via an insulatingfilm containing an organic material with a hygroscopic property and thelire. Therefore, various deteriorations caused by moisture and oxygensuch as contamination of the interior of the display device,deterioration of the electric characteristics, a dark spot, andshrinkage can be prevented, thereby enhancing the reliability of thedisplay device.

In addition, since a film constituting the display device and a filmused as a protective film are simultaneously formed by a same materialin the invention, the display device with high reliability can bemanufactured without increasing the number of steps.

The display device manufactured above comprises a structure of blockingcontaminants in a sealing region of an edge portion of a display device,and hence, the operational characteristics and reliability of thedisplay device can be improved sufficiently. Furthermore, electronicappliances using the display device of the present invention can exhibithigh degrees of reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a diagram showing a structure according to the presentinvention;

FIG. 2 is a diagram showing a structure according to the presentinvention;

FIG. 3 is a diagram showing a structure according to the presentinvention;

FIG. 4 is a diagram showing a structure according to the presentinvention;

FIG. 5 is a diagram showing a conventional structure;

FIG. 6 is a cross sectional view of a conventional EL display device;

FIG. 7 is a cross sectional view of a conventional EL display device;

FIGS. 8A to 8C are cross sectional views showing steps for manufacturingan active matrix substrate;

FIGS. 9A and 9B are cross sectional views showing steps formanufacturing an active matrix substrate;

FIG. 10 is a cross sectional view of a display device according to thepresent invention;

FIG. 11 is a cross sectional view of a display device according to thepresent invention;

FIGS. 12A to 12F are diagrams showing examples of a display device;

FIGS. 13A to 13C are diagrams showing examples of a display device;

FIG. 14 is a diagram showing a conventional structure;

FIG. 15 is a cross sectional view showing a display device according tothe present invention;

FIG. 16 is a cross sectional view of a display device according to thepresent invention;

FIG. 17 is a top view of a display device according to the presentinvention;

FIG. 18 is a cross sectional view of a display device according to thepresent invention;

FIGS. 19A and 19B are cross sectional views showing a display deviceaccording to the present invention;

FIGS. 20A and 20B are diagrams showing reliability evaluation of adisplay device according to the present invention; and

FIGS. 21A and 21B are diagrams showing reliability evaluation of adisplay device of a comparative example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention has been fully described by way of EmbodimentModes and Embodiments with reference to the accompanying drawings. Ashas been easily understood by the person skilled in the art, the presentinvention can be embodied in several forms, and the embodiment modes andits details can be changed and modified without departing from thepurpose and scope of the present invention. Accordingly, interpretationof the present invention should not be limited to descriptions mentionedin the foregoing embodiment modes and embodiments. Note that in thestructures according to the present invention described above, portionsidentical to each other or portions having a similar function arecommonly denoted by same reference numerals in the accompanying drawingssuch that additional descriptions are omitted.

Embodiment Mode 1

Preferred embodiment modes of the invention will hereinafter bedescribed with reference to the accompanying drawings.

FIG. 17 is a tow view of a display device according to the presentinvention. An edge portion of the display device taken along a line A-A′in FIG. 17 is described in FIG. 1. In FIG. 1, an, opening is formed inan insulating layer 12 containing an organic resin material, and theopening is covered with a protective film 14. A sealing material 13 isapplied over the protective film 14 so as to fill a depression due tothe opening. A substrate 10 comprising the depression and opposingsubstrate 11 are adhered (or bonded) to each other with the sealingmaterial 13. In the embodiment mode, the protective film 14 and wiringsare made of the same material through the same steps.

In Embodiment Mode 1, the opening is only formed in the insulating layercontaining the organic resin material. However another opening may beformed in an insulating layer on which a gate insulating film, aninterlayer film and the like are laminated, and may be covered with theprotective film and then the sealing material may be applied thereon. Ofcourse, the laminated film constituting the insulating layer may includea conductive film. In the present invention, such laminated film isreferred to as an insulating layer in the sense that the laminated layerincludes an organic resin material. On the insulating layer, a displayelement made of an organic light-emitting material is formed.

The insulating layer containing the organic resin material, which canserve as a path for contaminants, is isolated by the protective filminside the display device. Accordingly, the insulating layer isprotected with the sealing material and the protective film formedthereon, and therefore the contaminants cannot pentrate into theinterior of the display device even if outer edge portions of theinsulating layer in the display device are posed to the atmospheric airand moisture and oxygen exist outside of the display device penetrateinto the display device through a gap between the interlayer films orthe other films. Therefore, it is possible to prevent variousdeteriorations due to moisture, oxygen etc. such as contamination of theinterior of the display device, deterioration of the electriccharacteristics, a dark spot, and shrinkage, thereby improving thereliability of the display device. In addition, a film constituting thedisplay device and the protective film are simultaneously formed byusing a same material, and hence, the reliability of the display deviceto be manufactured can be further improved without increasing the numberof steps.

The protective film may be formed of one or more kinds of films selectedfrom thin conductive films and thin insulating films. As for the thinconductive films, a film made of one or more kinds of elements selectedfrom the group consisting of Al, Ti, Mo, W, and Si may be employed.Meanwhile, as for the thin insulating films, a film made of one or morekinds of materials selected from silicon nitride, silicon oxide, siliconoxynitride, aluminum nitride, aluminum oxynitride, aluminum nitrideoxide, aluminum oxide, diamond like carbon (DLC), a carbon nitride film((CN), siloxane polymer may be used.

The insulating layer may be made of a film comprising one or more kindsof materials selected from inorganic materials (such as silicon oxide,silicon nitride, silicon oxynitride, and silicon nitride oxide) andphotosensitive or nonphotosensitive organic resin materials (such aspolyimide, acrylic, polyamide, polyimide amide, resist,benzocyclobutene, and siloxane polymer), or a laminated layer of theseand the like. The siloxane polymer can be made of aninorganic-siloxane-based insulating material including a Si—O—Si bond,and an organosiloxane-based insulating material in which an organicradical such as methyl and phenyl is substituted for hydrogen bondedsilicon among compounds comprising silicon, oxygen, and hydrogen formedby using a siloxane-based material as a starting material.

Note that a plurality of openings may be formed in the insulating film.The plurality of openings may be partly or entirely covered with theprotective film and the sealing film. Further, each opening may beformed at any portion inside of the display device.

Although the opening is formed so as to contact with the glass substrate10 in FIG. 1 of the present embodiment mode, the structure of thepresent invention is not limited to the structure. That is, theinsulating film containing an organic material having a hygroscopicproperty and the like may be covered with the protective film, and adepression due to the formation of the opening may be filled with thesealing material so as to seal the opening, and therefore, the openingmay be formed until the opening reaches to a film having dense structuresuch as a silicon nitride film.

Meanwhile, two or more protective films may be formed as a firstprotective film 34 and a second protective film 35 as depicted in FIG. 3rather than only one protective film. In FIG. 3, a substrate 30 and anopposing substrate 31 are bonded to each other with a sealing material33, and an insulating layer 32 on the substrate is isolated by theprotective films 34 and 35. In order to prevent short circuit in the sointerior of the insulated display device, a portion to be covered withthe protective film is necessary to be designed by a mask etc. When theinsulating layer is shielded with the two-layered protective films, theeffect of blocking the contaminants can be further improved as comparedwith the case of using a single-layer protective film.

Further, the inclined surface of the opening is desirably smooth. Whenthe inclined surface of the opening is not smooth, the protective filmcovering the surface thereof is affected by the unevenness on thesurface of the opening. The protective film is destroyed in the portionof thinner film thickness. The contaminants cannot be blockedsufficiently by such destroyed protective film, thereby reducing theadvantageous effect of the present invention. Accordingly, when theopening has a smooth surface, favorable coverage of the protective filmlaminated on the opening can be obtained, thereby improving theadvantageous effect of the present invention. Therefore, it ispreferable to perform wet etching on a film to form an opening thereonby using a photosensitive material such that unevenness formed on thesurface of the film is reduced and its smoothness of the surface isimproved.

As set forth above, the display device in which the frame of the displaydevice is narrowed and the contaminants due to the deterioration areblocked can be obtained.

Embodiment Mode 2

Another embodiment mode of the present invention will hereinafter bedescribed in more detail with reference to the accompanying drawings.

FIG. 17 is a top view of a display device according to the presentinvention. An edge portion of the display device taken along a line A-A′in FIG. 17 is illustrated in FIG. 2. In FIG. 2, a plurality of openingsis formed in an insulating layer 22 containing an organic resinmaterial. The surface of the insulating layer 22 comprised depressionsand projections. Each opening is covered with a protective film 24. InEmbodiment Mode 2, an opposing substrate 21 attached to the substrate 20is also comprises depressions and projections in the direction of thesubstrate 20 side. The opposing substrate 21 and the substrate 20 areadhered (or bonded) to each other with a sealing material 23 such thatthe depressions and the corresponding projections of each substrate arematched with each other.

Since the substrate 20 comprising the insulating layer and the opposingsubstrate 21 are bonded to each other such that the respectivedepressions and projections thereof are matched with each other, thesealing material sandwiched therebetween is pressed and extended to thegap between the depressions and projections to bond the substrates.Accordingly, when minute amounts of moisture and oxygen intrude from thesealing material, since the moisture and oxygen have to move through along zigzag path along the depressions and projections, they hardlypenetrate into the interior of the display device. As a result, theeffect of blocking the contaminants can be improved, thereby providing adisplay device having high reliability. In this embodiment mode, theprotective film and a wiring are made of the same material through thesame steps.

The number of the depressions and projections formed on the substrate 20comprising the insulating layer and the opposing substrate 21 is notlimited. Further how to fit the depressions into the correspondingprojections is not limited to the present embodiment mode, and thedepressions may face each other while the projections may face eachother, or the depressions may be fit into the corresponding projections,respectively.

The depressions and projections formed on the opposing substrate may beformed by processing the substrate, or a film having the depressions andprojections may be formed on the opposing substrate. The film having thedepressions and projections is preferably made of a substance which canblock the contaminants as well as the protective film.

The protective film 24 may be made of one kind or plural kinds of filmsselected from thin conductive films and thin insulating films. As thethin conductive films, a film made of one kind or plural kinds ofelements selected from the group consisting of Al, Ti, Mo, W, and Si maybe used. Meanwhile, as the thin insulating films, a film made of onekind or plural kinds of materials selected from silicon nitride, siliconoxide, silicon oxynitride, aluminum nitride, aluminum oxynitride,aluminum nitride oxide, aluminum oxide, diamond like carbon (DLC), acarbon nitride film (CN), so siloxane polymer may be used.

The insulating layer may be made of a film comprising one or more kindsof materials selected from inorganic materials (such as silicon oxide,silicon nitride, silicon oxynitride, and silicon nitride oxide) andphotosensitive or nonphotosensitive organic resin materials (such aspolyimide, acrylic, polyamide, polyimide amide, resist,benzocyclobutene, and siloxane polymer), or a laminated layer of theseand the like.

In Embodiment Mode 2, each opening is formed only in the film containingthe organic resin material. In addition to that, the openings may beformed in an insulating layer with a gate insulating film, an interlayerfilm and the like laminated thereon, and covered with the protectivefilm and then applied with the scaling material. Of course, thelaminated film constituting the insulating layer may comprise aconductive film. In the present invention, such laminated film isreferred to as an insulating layer at least in the sense that thelaminated layer includes the organic resin material. On the insulatinglayer, a display element made of an organic light-emitting material isformed.

The insulating layer containing the organic resin material, which canserve as a s path for contaminants, is isolated by the protective filmin the interior of the display device. Accordingly, the insulating layeris shielded with the sealing material and the protective film formedthereon, and therefore the contaminants cannot penetrate into theinterior of the display device even if outer edge portions of theinsulating layer in the display device are exposed to the atmosphericair and moisture and oxygen exist outside of the display devicepenetrate into the display device through the gap between the interlayerfilms or the other films. Therefore, it is possible to prevent variousdeteriorations due to moisture, oxygen and the like such ascontamination of the interior of the display device, deterioration ofthe electric characteristics, dark spots, and shrinkage, therebyimproving the reliability of the display device. In addition, a filmconstituting the display device and the protective film aresimultaneously formed by using the same material, and hence, thereliability of the display device to be manufactured can be fartherimproved without increasing the number of steps.

The organic resin materials such as acrylic, polyamide, and polyimidemay be used for the insulating layer, and the materials for theinsulating layer is not limited thereto.

A plurality of openings may be formed in the insulating layer, and theopenings may be partly or entirely covered with the protective film andthe sealing material. The openings may be formed at any portion in theinterior of the display device.

Although the openings are formed so as to contact with the glasssubstrate 20 in FIG. 2 of the present embodiment mode, the structure ofthe present invention is not limited thereto. That is, the insulatingfilm containing an organic material having a hygroscopic property may becovered with the protective film, and the depressions due to theformation of the openings may be filled with the sealing material so asto seal the openings, and therefore, the openings may be formed untilthe opening reaches to a film having dense structure such as a siliconnitride film.

Meanwhile, not only one protective film but also two or more protectivefilms may be formed as depicted in FIG. 4. In FIG. 4, a substrate 40 andan opposing substrate 41 are bonded to each other with a scalingmaterial 43, and an insulating layer 42 on the substrate is isolated bya protective films 44 and 45. In order to prevent short circuit in theinsulated display device, when the insulating film is covered with aconductive film, a portion to be covered with the protective film isnecessary to be designed by a mask etc. When the insulating layer isshielded with the two-layer protective films, the effect of blocking thecontaminants can be further improved as compared with the case of usinga one-layer protective film.

Further, inclined surfaces of the openings covered with the protectivefilms are desirably smooth. When the inclined surfaces of the openingsare not smooth, the protective films covering the surface thereof areaffected by the shape of the unevenness on the surfaces. The protectivefilms are destroyed in the portion of thin film thickness. Thecontaminants cannot be sufficiently blocked by such destroyed protectivefilm, and the advantageous effect of the present invention is lessened.Accordingly, when the openings have smooth surfaces, favorable coverageof the protective films formed thereon can be obtained, therebyimproving the advantageous effect of the present invention. Therefore,it is preferable to perform wet etching on a film to form an openingthereon by using a photosensitive material such that unevenness formedon the so surface of the film is reduced and its smoothness of thesurface is improved.

As set forth above, the display device with high reliability in whichthe frame of the display device is narrowed and the contaminants causingvarious deteriorations are blocked can be obtained.

Embodiment Embodiment 1

In Embodiment 1, an example of manufacturing a display device having adual emission structure according to the present invention willhereinafter be described. In the present invention, a display panel inwhich an EL element formed on a substrate is to sealed between thesubstrate and a covering material and a display module comprising TFTsin the display panel are generically referred to as the display device.The EL element comprises a layer including an organic compound thatgenerates electroluminescence (a light emitting layer), an anode layer,and a cathode layer. Luminescence obtained from organic compounds isclassified into light emission upon returning to the base state fromsinglet excited state (fluorescence) and light emission upon returningto the base state from triplet excited state (phosphorescence). ELmaterials, which can be used for the present invention, include alllight-emitting materials that emit photons via either the singletexcited state or the triplet excited state, or via each excited state.

In the present invention, all the layers that are formed between ananode and a cathode in an EL element are collectively defined as alight-emitting layer. Specifically, the light-emitting layer includes anEL layer, a hole injecting layer an electron injecting layer, a holetransporting layer an electron transporting layer, etc. Basically, theEL element comprises a structure in which an anode layer, an EL layer,and a cathode layer are sequentially laminated. In addition to that, theEL element may also comprises a structure in which an anode layer, ahole injecting layer, an EL layer, a cathode layer, etc. aresequentially laminated, or another structure in which an anode layer ahole injecting layer, an EL layer, an electron transporting layer acathode layer, etc. are sequentially laminated.

As a base film 301, a silicon oxynitride film with a thickness of from10 nm to 200 nm (preferably, from 50 nm to 100 nm) is formed on asubstrate 300 having an insulated surface, and a silicon nitride oxidefilm with a thickness of form 50 nm to 200 nm (preferably, from 100 nmto 150 nm) is laminated thereon by plasma CVD. In this embodiment, thesilicon oxynitride film with a thickness of 50 nm and the siliconnitride oxide film with a thickness of 100 nm are formed by plasma CVD.As for the substrate 300, a glass substrate, a quartz substrate, asilicon substrate, a metal substrate, or a stainless substrate each ofwhich has an insulated surface on a surface thereof may be used. Inaddition, a plastic substrate or a flexible substrate, which canwithstand processing temperatures of this embodiment, may be used.Further, a two-layer structure may be adopted as the base film, and asingle-layer film or a laminated structure having more than two layersof the base (insulating) film may also be adopted.

Subsequently, a semiconductor film is formed on the base film. Thesemiconductor film may be formed to have a thickness of from 25 nm to200 nm (preferably, from 30 nm to 150 nm) by a known technique(sputtering, LPCVD, plasma CVD, and the like). A material for thesemiconductor film is not particularly limited, however, thesemiconductor film is preferably formed of silicon or a silicongermanium (SiGe) alloy.

In this embodiment, an amorphous silicon film is formed as thesemiconductor film to have a thickness of 54 nm by plasma CVD. In thisembodiment, the amorphous silicon film is crystallized by thermalcrystallization and laser crystallization with the use of a metalelement for promoting crystallization. Alternatively, withoutintroducing the metal element into the amorphous silicon film, hydrogenincluded in the amorphous silicon film may be released to lower hydrogenconcentration to 1×10²⁰ atoms/cm³ or less by heating under a nitrogenatmosphere at a temperature of 500° C. for one hour. Thereafter, thelaser crystallization may be performed. The dehydrogenation is performedbecause the amorphous silicon film is damaged by laser irradiation whenthe film contains much hydrogen.

Nickel is used as the metal element, and is doped into the amorphoussilicon film by solution application. The method of doping the metalelement into the amorphous silicon film is not particularly limited oncondition that the metal element can exist on the surface of or insidethe amorphous silicon film. For example, a method such as sputtering,CVD, plasma processing (including plasma CVD adsorption, and a methodfor applying a metal salt solution can be employed. Among them, themethod using the metal salt solution is simply and easily performed, andis useful for easily adjusting concentration of the metal element. Atthis time, an oxide film is preferably formed by ultraviolet (UV) rayirradiation under an oxygen atmosphere, thermal oxidation, treatmentwith ozone water or hydrogen peroxide including hydroxyl radical, andthe like in order to improve wettability of the surface of an amorphoussemiconductor film and to spread aqueous solution over an entire surfaceof the amorphous silicon film.

Subsequently, a heat treatment is performed at temperatures of from 500°C. to 550° C. for from 4 hours to 20 hours to crystallize the amorphoussilicon film. In this embodiment, after forming a metal-containing layerby solution application with the use of nickel as the metal element, themetal-containing layer is introduced on the amorphous silicon film, andheat treatment is performed thereto at a temperature of 550° C. for fourhours, thereby obtaining a first crystalline silicon film.

Next, the first crystalline silicon film is irradiated with laser beamto promote crystallization, and therefore a second crystalline siliconfilm is obtained. Laser crystallization is performed by irradiatinglaser beam to the semiconductor film. A solid-state laser, a gas laseror a metal laser of continuous oscillation is preferable to be used forthe laser crystallization. The solid-state laser includes: YAG laser,YVO₄ laser, YLF laser, YAlO₃ laser, glass laser, ruby laser, alexandritelaser, Ti:sapphire laser, and the like of continuous oscillation. Thegas laser includes: Ar laser, Kr laser, CO₂ laser, and the like ofcontinuous oscillation. The metal laser includes: helium cadmium laser,copper vapor laser, and gold vapor laser of continuous wave oscillation.Note that an excimer laser of continuous light emission can also beapplied. The laser beam may be converted to higher harmonics by anonlinear optical device. A crystal used for the nonlinear opticaldevice such as LBO, BBO, KDP, KTP, KB5, and CLBO is superior inconversion efficiency. The conversion efficiency can be drastically soincreased by introducing such nonlinear optical device into a laserresonator. A laser of the higher harmonics is typically doped with Nd,Yb, Cr, and the like, and these are excited to oscillate laser beam. Thetype of a dopant may be appropriately selected by those who operate thepresent invention.

For example, the semiconductor film may be made of a material asfollows: an amorphous semiconductor (hereinafter referred to as “AS”)manufactured by vapor phase growth or sputtering with the use ofsemiconductor material gas represented by silane, germanium etc.; apolycrystalline semiconductor manufactured by crystallizing theamorphous semiconductor with the use of light energy, thermal energyetc.; a semi-amorphous (which is also referred to as a microcrystal)semiconductor (hereinafter referred to as “SAS”), and the like.

The SAS is a semiconductor which comprises an intermediate structurebetween an amorphous structure and a crystalline structure (includingsingle crystal and poly crystal), and a third stable state in view offree energy. The SAS further includes a crystalline region having ashort-range order along with lattice distortion. A crystalline region ina range of from 0.5 nm to 20 nm can be observed in a part of the regionamong the semi-amorphous semiconductor film. In the case where thesemi-amorphous semiconductor film contains silicon as its principalconstituent, the Raman spectrum is shifted to a lower wavenumber sidethan 520 cm⁻¹. The diffraction peak of (111) and (220) which is believedto be originated in a crystalline silicon lattice, is observed in thesemi-amorphous semiconductor film by X-ray diffraction. Further, thesemi-amorphous semiconductor film is added with at least 1 atom % ofhydrogen or halogen as a naturalizing agent for dangling bonds. The SASis formed by glow discharge decomposition with silicide gas (by plasmaCVD). As for the silicide gas, in addition to SiH₄, Si₂H₆, SiH₂Cl₂,SiHCl₃, SiC₄, SiF₄, and the like can be used. Furthermore, GeF₄ may bemixed in the above-mentioned gases for the silicide gas. The silicidegas may also be diluted in one or more rare gas elements selected fromthe group consisting of H₂, a mixture of H₂ and He, Ar, Kr, and Ne. Thedilution ratio is in the range of 1:2 to 1:1,000. The pressure isapproximately in the range of from 0.1 Pa to 133 Pa. The power supplyfrequency is in a range of from 1 MHz to 120 MHz, preferably 13 MHz to60 MHz. The substrate heating temperature may be at most at 300° C. Asfor the impurity element in a film, respective concentrations ofimpurities of atmospheric constituents such as oxygen, nitrogen, orcarbon are preferably set to 1×10²/cm⁻¹ or less; in particular, theoxygen concentration is set to 5×10¹⁹/cm³ or less, more preferably,1×10¹⁹/cm³ or less. Note that, a compound semiconductor film having anamorphous structure such as an amorphous silicon germanium film, and anamorphous silicon carbide film may also be employed.

The crystalline semiconductor film thus obtained is patterned by apatterning treatment using photolithography so as to form semiconductorlayers 305 to 308.

After forming the semiconductor layers 305 to 308, minute amounts ofimpurity elements (boron or phosphorous) may be doped to control athreshold value of a TFT.

Subsequently, a gate insulating film 309 covering the semiconductorlayers 305 to 308 is formed. The gate insulating film 309 is formed ofan insulating film including silicon to have a thickness of from 40 nmto 150 nm by plasma CVD or sputtering. In this embodiment, a siliconoxynitride film is formed to have a thickness of 115 nm by plasma CVD.The material for the gate insulating film is not limited to the siliconoxynitride film, and other insulating films with a single layerstructure or a laminated structure may be used.

A first conductive film with a film thickness of from 20 nm to 100 nmand a second conductive film with a film thickness of from 100 nm to 400nm are formed and laminated over the gate insulating film. The first andthe second conductive films may be made of an element selected from Ta,W, Ti, Mo, Al, and Cu, or an alloy material or a compound materialhaving the foregoing element as a main component. A semiconductor filmrepresented by a polycrystalline silicon film that is doped with animpurity element such as phosphorus or an AgPdCu alloy may be used asthe first and the second conductive films. The conductive films are notlimited to a two-layer structure, and, for example, a three-layerstructure in which a 50-nm-thick tungsten film, a 500-nm-thick alloy(Al—Si) film of aluminum and silicon, and a 30-nm-thick titanium nitridefilm are sequentially laminated may be applied. In the case of thethree-layer structure, tungsten nitride may be used as substitute fortungsten of the first conductive film; an alloy (Al—Ti) film of aluminumand titanium may be used as substitute for an alloy (Al—Si) film ofaluminum and silicon of the second conductive film; or a titanium filmmay be used as substitute for a titanium nitride film of a thirdconductive film. Further, a single layer structure may also be applied.In this embodiment, a tantalum nitride film 310 of 30 nm in thicknessand a tungsten film 311 of 370 nm in thickness are sequentiallylaminated over the gate insulating film 309 (FIG. 8A).

Next, a mask comprising a resist is formed by photolithography, and afirst etching treatment is performed to form an electrode and a wiring.The first conductive film and the second conductive film can be etchedinto a desired tapered shape by appropriately adjusting etchingconditions (such as electric energy applied to a coil-shaped electrode,electric energy applied to an electrode on a substrate side, andtemperature of the electrode on the substrate side) with the used of ICP(Inductively Coupled Plasma) etching. For an etching gas, achlorine-based gas typified by Cl₂, BCl₃, SiCl₄, CCl₄ and the like; afluorine-based gas typified by CF₄, SF₆, NF₃ and the like; or O₂ can beappropriately used.

A first-shape conductive layer (a first conductive layer and a secondconductive layer) comprising the first conductive layer and the secondconductive layer is formed by the first etching treatment.

Subsequently, a second etching treatment is performed without removing amask made of resist. Here, a W film is etched selectively. Then, thesecond conductive layers 322 b to 326 b are formed by the second etchingtreatment. On the other hand, the first conductive layers 322 a to 326 aare hardly etched, and second-shape conductive layers 322 to 326 areformed (FIG. 8B).

An impurity element imparting n-type conductivity is added to thesemiconductor layer in low concentration by performing a first dopingtreatment without removing the mask made of the resist. The dopingtreatment may be performed by ion doping or ion implantation. An elementbelonging to Group 15 in the periodic table, typically phosphorus (P) orarsenic (As) is used for the impurity element imparting n-typeconductivity, and phosphorus (P) is used here. In this case, thesecond-shape conductive layers 322 to 326 serve as masks for preventingthe impurity element imparting n-type conductivity from being doped intothe semiconductor layer, and an impurity region is formed in aself-aligning manner. The impurity region is doped with the impurityelement imparting n-type conductivity in a concentration range of from1×10¹⁸ atoms/cm³ to 1×10²⁰ atoms/cm³.

After removing the mask made of the resist, another mask made of aresist is newly formed, and a second doping treatment is performed at ahigher accelerating voltage than the first doping treatment. The seconddoping treatment is performed by using the second conductive layers 323b and 326 b as masks for preventing the impurity element from dopinginto the semiconductor layer so as to add the impurity element to thesemiconductor layer below the tapered portion of the first conductivelayers 322 a to 326 a. Subsequently, a third doping treatment isperformed at a lower accelerating voltage than the second dopingtreatment. According to the second doping treatment and the third dopingtreatment, a lower concentration impurity region 335 overlapping thefirst conductive layer is added with the impurity element impartingn-type conductivity in a concentration range of from 1×10¹⁸ atoms/cm³ to5×10¹⁹ atoms/cm³, and higher concentration impurity regions 334 and 337are added with the impurity element imparting n-type conductivity in aconcentration range of from 1×10¹⁹ atoms/cm³ to 5×10²¹ atoms/cm³.

Of course, the lower concentration impurity region and the higherconcentration impurity regions can be formed by once doping treatmentwith a combination of the second doping treatment and the third dopingtreatment by setting an accelerating voltage appropriately.

Next, after removing the mask made of the resist, still another maskmade of a resist is newly formed, and a fourth doping treatment iscarried out. According to the fourth doping treatment, impurity regions343, 344, 347, and 348 that are added with an impurity element impartinga conductivity type opposite to the previously doped conductivity typeare formed in the semiconductor layers to be active layers of ap-channel TFT. The impurity regions are formed in a self-aligning mannerby using the second-shape conductive layers 322 and 326 as masks forpreventing the impurity element from doping into the semiconductor layerand by adding an impurity element imparting p-type conductivity. In thisembodiment, the impurity regions 343, 344, 347, and 348 are formed byion doping using diborane (B₂H₆). In the case of the fourth dopingtreatment, a semiconductor layer forming an n-channel TFT is coveredwith the mask made of the resist. According to the first to third dopingtreatments, the impurity regions are doped with phosphorus in differentconcentrations, respectively. However, any problems do not arise sincethe impurity regions function as a source region and a drain region of ap-channel TFT by carrying out the doping treatments so as to have aconcentration of an impurity element imparting p-type conductivity offrom 1×10¹⁹ atoms/cm³ to 5×10²¹ atoms/cm³.

According to the above-described steps, the impurity regions are formedin each semiconductor layer (FIG. 8C).

Subsequently, the mask comprising the resist is removed, and aninsulating film 349 is formed as a passivation film. The insulating film349 is formed of an insulating film including silicon with a thicknessof from 100 nm to 200 nm by plasma CVD or sputtering (FIG. 9A). Ofcourse, the insulating film 349 is not limited to a silicon oxynitridefilm, and other insulating films including silicon and having a singlelayer structure or a laminated structure may be adopted. In thisembodiment, a silicon oxynitride film of 150 nm in thickness is formedby plasma CVD.

Moreover, a step of hydrogenating the semiconductor layers is performedby heat treatment at temperatures of from 300° C. to 550° C. for 1 hourto 12 hours under a nitrogen atmosphere. The step is preferablyperformed at temperatures of from 400° C. to 500° C. The step is a stepfor terminating dangling bonds of the semiconductor layers due tohydrogen contained in the first insulating film 349. In this embodiment,the heat treatment is performed at 410° C. for one hour.

The insulating film 349 is formed of a material selected from siliconnitride, silicon oxide, silicon oxynitride (SiON), silicon nitride oxide(SiNO), aluminum nitride (AlN), aluminum oxynitride (AlON), aluminumnitride oxide having more nitrogen content than oxygen content (AlNO),aluminum oxide, diamond like carbon (DLC), and a carbon nitride (CN)film.

In the present invention, a silicon oxynitride (SiON) film denotes afilm containing Si of from 25 atom % to 35 atom %, oxygen of from 55atom % to 65 atom %, nitrogen of from 1 atom % to 20 atom %, andhydrogen of from 0.1 atom % to 10 atom %. Meanwhile, a silicon nitrideoxide (SiNO) film denotes a film including Si of from 25 atom % to 35atom %, oxygen of from 15 atom % to 30 atom %, nitrogen of from 20 atom% to 35 atom %, and hydrogen of from 15 atom % to 25 atom %.

In order to activate the impurity element, heat-treatment, irradiationof intense light, or irradiation of laser beam may be carried out.Simultaneously with the activation, plasma damage in the gate insulatingfilm or plasma damage in an interface between the gate insulating filmand the semiconductor layer can be repaired.

An interlayer film 350 containing an organic resin material is formed onthe insulating film 349. As the interlayer film 350, a film comprisingone kind of or plural kinds of materials selected from inorganicmaterials (such as silicon oxide, silicon nitride, silicon oxynitride,and silicon nitride oxide) and photosensitive or nonphotosensitiveorganic materials (or organic resin materials) (such as polyimide,acrylic, polyamide, polyimide amide, resist, benzocyclobutene, andsiloxane polymer), or a laminated layer of these and the like can beused. Further, a negative type photosensitive organic material thatbecomes insoluble in etchant by photosensitive light, and a positivetype photosensitive organic material that becomes soluble in etchant bylight, can be also used as the interlayer film. In this embodiment, theinterlayer film 350 is made of a positive photosensitive acrylic that isthe photosensitive organic resin material. A curved surface having acurvature radius (0.2 μm to 3.0 μm) only in an upper edge portion of theinterlayer film is preferably provided in the case of using the positivephotosensitive acrylic. Thereafter, a passivation film made of thefollowing materials may be formed on the interlayer film 350: siliconnitride; silicon oxide; silicon oxynitride (SiON); silicon nitride oxide(SiNO); aluminum nitride (AlN); aluminum oxynitride (AlON); aluminumnitride oxide having more nitrogen content than oxygen content (AlNO);aluminum oxide; diamond like carbon (DLC); a carbon nitride (CN) film;or siloxane polymer.

Subsequently, the interlayer film 350, the insulating film 349, and thegate insulating film 309 are etched to form openings that are in contactwith a source region and a drain region. In order to form the openings,the insulating film 349 and the gate insulating film may be etched bynewly forming a mask after etching the interlayer film or by using theetched interlayer film 350 as the mask. Then, a metal film is formed andetched so as to form a source electrode or drain electrode 352, and eachwiring (not shown) for electrically connecting to each impurity region,respectively. The metal film may be made of a film comprising an elementof aluminum (Al), titanium (Ti), molybdenum (Mo), tungsten (W), prsilicon (Si), of an alloy film comprising these elements. In thisembodiment, after laminating a titanium film/a silicon-aluminum alloyfilm/a titanium film (Ti/Si-Al/Ti) to be 100 nm/350 nm/100 nm inthickness respectively, the source electrode or drain electrode 352 andeach wiring (not shown) are formed by patterning and etching thelaminated film into a desired shape.

In this embodiment, after forming the interlayer film 350, an opening1018 connecting to the substrate 300 is formed in a sealing region. Aprotective film 1019 is formed so as to cover the opening 1018. Theprotective film 1019 and the source electrode or drain electrode 352 aremade of the same material through the same processing step.

Subsequently, a pixel electrode 353 is formed. In this embodiment, atransparent conductive film is formed and etched into a predeterminedshape to form the pixel electrode 353 (FIG. 8B).

As for the transparent conductive film, for example, a compound ofindium oxide and tin oxide, a compound of indium oxide and zinc oxide,zinc oxide, tin oxide, or indium oxide can be used. A transparentconductive film doped with gallium may also be used. The pixel electrode353 may be formed on a flat interlayer insulating film prior to theformation of the above-mentioned wirings. It is effective to planarize astep due to a TFT by using a planarizing film comprising resin. Since anEL layer to be formed later is very thin, the step may cause a defect inlight emission. Consequently, the step is preferably leveled beforeforming the pixel electrode so as to form the EL layer on a surface assmooth as possible.

According to the above-described steps, an active matrix substratecomprising so a TFT is completed. In this embodiment, the active matrixsubstrate comprises a double gate structure in which two channelformation regions are formed in the n-channel TFT of the pixel region.Furthermore, the active matrix substrate may comprise a single gatestructure having one channel formation region or a triple gate structurehaving three channel formation regions. Although a TFT for the drivingcircuit portion comprises a single gate structure in this embodiment,the TFT may have a double gate structure or a triple gate structure.

Not limited to a method for manufacturing a TFT described in thisembodiment, the present invention can be applied to a top gate type(planar type), a bottom gate type (inversely staggered type), or a dualgate type having two gate electrodes disposed above and below a channelregion while interposing a gate insulating film therebetween.

As shown in FIG. 10, an insulator 1012 is formed after forming the pixelelectrode 353. The insulator 1012 may be formed by patterning aninsulating film or an organic resin film including silicon with athickness of from 100 nm to 400 nm.

Since the insulator 1012 is an insulating film, electrostatic dischargedamage to a device in deposition needs attention. In this embodiment,the resistivity is reduced by adding a carbon particle or a metalparticle into an insulating film to be a material of the insulator 1012,thereby suppressing generation of static electricity. At this time, theamount of a carbon particle or a metal particle to be added may beadjusted such that the resistivity becomes from 1×10⁶ Ωm to 1×10¹² Ωm(preferably from 1×10⁸ Ωm to 1×10¹⁰ Ωm).

An EL layer 1013 is formed on the pixel electrode 353. Only one pixel isshown in FIG. 10; however, in this embodiment, EL layers correspondingto respective colors of R (red), G (green), and B (blue) are formedseparately. In this embodiment, a low molecular weight organiclight-emitting material is formed by vapor deposition. Specifically, theEL layer has a laminated structure having a copper phthalocyanine (CuPc)film provided with a thickness of 20 nm as the hole injecting layer anda tris-8-quinolinolato aluminum complex (Alq₃) film provided thereuponwith a thickness of 70 nm as the EL layer. Colors of light emission canbe controlled by adding fluorescent dye such as quinacridone, perylene,or DCM 1 to Alq₃.

However, the foregoing example is one example of the organiclight-emitting material, which can be used as the EL layer and theorganic light-emitting material is not necessarily limited thereto. TheEL layer (layer for light emission and for carrier movement for thelight emission) may be formed by freely combining the EL layer thecharge transporting layer and the charge injecting layer. Although theexample in which the low molecular weight organic light-emittingmaterial is used as the EL layer is described in this embodiment, forexample, an intermediate molecular weight organic light-emittingmaterial or a high molecular weight organic light-emitting material maybe used as substitute for the low molecular weight organiclight-emitting material. Throughout the present specification, anorganic light-emitting material which does not sublimate and hasmolecularity of equal to or less than 20 or a molecular chain length ofequal to or less than 10 μm is defined as the intermediate molecularweight organic light-emitting material. In addition, as an example ofusing the high molecular weight organic light-emitting material, alaminated structure having a polythiophene (PEDOT) film provided by spincoating with a thickness of 20 nm as the hole injecting layer and aparaphenylene-vinylene (PPV) film with a thickness of approximately 100nm provided thereupon as the EL layer may be given. In addition,emission wavelength can be selected from red through blue by usingm-conjugated polymer of PPV. An inorganic material such as siliconcarbide can be used for the charge transporting layer and the chargeinjecting layer. These organic light-emitting materials and inorganicmaterials can be made of known materials.

Next, a cathode 1014 comprising a conductive film is provided on the ELfilm 1013. The cathode 1014 may be made of a material having lower workfunction (for example, Al, Ag, Li, and Ca, or alloy of these elementssuch as MgAg, MgIn, AlLi, CaF₂, and CaN). In the present embodiment, thecathode 1014 is formed by laminating a thin metal film (MgAg: 10 nm inthickness), a 110-nm-thick transparent conductive film (such as ITO(indium tin oxide alloy), indium zinc oxide alloy, zinc oxide, tinoxide, and indium oxide) such that light generated in the EL layerpasses through the cathode.

An EL element 1015 is completed at the time of forming up to the cathode1014. The EL element 1015 is made of the pixel electrode (anode) 353,the EL layer 1013, and the cathode 1014.

It is effective to provide a passivation film 1022 so as to completelycover the EL device 1015. The passivation film is made of an insulatingfilm including an element as follows: silicon nitride; silicon oxide;silicon oxynitride (SiON); silicon nitride oxide (SiNO); aluminumnitride (AlN); aluminum oxynitride (AlON); aluminum nitride oxide (AlNO)containing more nitrogen content than oxygen content; aluminum oxide;diamond like carbon (DLC); a carbon nitride film (CN); or siloxanepolymer. The passivation film may be formed by the single-layerinsulating film or a laminated layer of these insulating films.

In such the case, a film favorable in coverage is preferably used as thepassivation film. It is effective to use a carbon film, particularly aDLC film. Since the DLC film can be formed in a temperature range offrom room temperature to equal to or less than 100° C., the DLC film canbe easily formed above the EL layer 1013 having low heat resistance. TheDLC film has a high blocking effect to oxygen and can suppressoxidization of the EL layer 1013. Consequently, a problem of oxidationof the EL layer 1013 during the following sealing step can be avoided.

According to the embodiment, in the sealing region, the sealing material1017 is applied on the protective film 1019 so as to fill thedepressions generated due to the openings, thereby adhering (bonding)the substrate 300 and the covering material 1021. In this embodiment,the protective film 1019 and the wirings are made of the same materialthrough the same step.

The material for a scaling material 1017 is not particularly limited,and the scaling material is preferably made of typical visible lightcurable resin, ultraviolet curable resin, or thermal curable resin. Inthis embodiment, thermal curable epoxy resin is used for the sealingmaterial 1017. Further, the covering material 1021 is made of a glasssubstrate, a quartz substrate, a plastic substrate (including a plasticfilm), or a flexible substrate with carbon films (more preferably, a DLCfilm or a CN film) formed on each surface thereof. Aluminum films (suchas AlON, AlN, and AlO), SiN, and the lie can be used as well as thecarbon films.

Thus, a dual emission display device, which can emit light in an upwarddirection and a downward direction, having a structure as shown in FIG.10 is completed. A region in which the edge portion of the insulatinglayer of the display device is exposed in FIG. 10 is covered with theprotective film 1019 in FIG. 15. In FIG. 15, reference numeral 1500 is asubstrate, reference numeral 1550 is an interlayer insulating film,reference numeral 1552 is an electrode, reference numeral 1512 is aninsulating film, reference numeral 1515 is a pixel electrode, referencenumeral 1513 is an EL layer reference numeral 1514 is a cathode,reference numeral 1553 is an EL element, and reference numeral 1530 is apassivation film. In a sealing region, an opening portion 1518 is formedat the side of the substrate 1500, and the opening portion 1518 iscovered with a protective film 1519. The substrate 1500 and a covermember 1521 are adhered with each other by a sealing member 1517. InFIG. 15 of the present invention, the openings and the edge portion ofthe insulating layer are covered with the same protective film 1519.However, each opening and the edge portion of the insulating layer maybe covered with different protective films, respectively. According tothe structure in FIG. 15, intrusion of the contaminants into theinterior of the display device can be further prevented, therebyenhancing the reliability of the display device.

It is effective to continuously carry out the steps of up to forming thepassivation film after forming the insulator 1012 by using a depositionapparatus having a multi-chamber system (or an in-line system) withoutexposure to the atmosphere. In addition, with further development, thesteps of up to sealing with the covering material 1021 can be carriedout without exposure to the atmospheric air.

By providing an impurity region overlapping a gate electrode with aninsulating film therebetween, an n-channel TFT resistive todeterioration resulting from a hot-carrier effect can be formed.Consequently, a semiconductor device with high reliability can berealized.

In this embodiment, only a structure of a pixel portion and a drivingcircuit is shown. However according to the manufacturing steps in thisembodiment, logic circuits such as a signal division circuit, a D/Aconverter, an operation amplifier, and a γ-correction circuit can bealso formed on the same insulator. Furthermore, a memory or amicroprocessor can be formed thereon.

In this embodiment, the opening 1018 is formed in the insulating layerincluding the organic resin material and the surface thereof is coveredwith the protective film 1019. Therefore, the insulating layer thatbecomes a path for the contaminants is isolated, which prevents thecontaminants from penetrating into a display element. In the case wherethe protective film 1019 is made of a conductive film, it is necessaryto design a portion to be covered with the protective film by a masketc. so as to prevent a short circuit inside the display device. Asshown in FIG. 4, when the insulating layer is isolated by the protectivefilm with a laminated structure for covering the openings, the effect ofblocking the contaminants is further improved as compared with the caseof using the protective film with a single layer.

According to the present invention, the path for moisture, which is theinsulating layer containing the organic resin material of the displaydevice is shut out. As a result, it is possible to prevent moisture andoxygen exist outside of the display device from penetrating into adisplay element inside the display device via the insulating film havinga hygroscopic organic material and the like. Therefore, variousdeteriorations caused by moisture and oxygen such as contamination ofthe interior of the display device, deterioration in the electriccharacteristics, a dark spot, and shrinkage can be prevented, therebyenhancing the reliability of the display device. In addition, since afilm made of the same material as the film constituting the displaydevice is used as the protective film for covering the openings, adisplay device with high reliability can be manufactured withoutincreasing the number of the steps.

Embodiment 2

In Embodiment 2, an example of a display device manufactured accordingto Embodiment 1, which has a different structure in a sealing regionfrom that in Embodiment 1, will be described with reference to FIG. 11.

In FIG. 11, reference numeral 1100 denotes a substrate, referencenumeral 1101 denotes an electrode, reference numeral 1111 denotes apixel electrode, reference so numeral 1112 is an insulating film,reference numeral 1113 denotes an EL layer, reference numeral 1114denotes a cathode, reference numeral 1115 denotes an EL element, andreference numeral 1130 denote a passivation film. In a scaling region,depressions 1121 a, 1121 b and 1121 c are formed at the side of thesubstrate 1100 by openings 1125 a, 1125 b, and 1125 c and a protectivefilm 1118 for covering the openings. At the side of the coveringmaterial 1123, projections 1122 a, 1122 b, and 1122 c are formed byinsulators 1120 a, 1120 b, and 1120 c, and another protective film 1117for covering the insulators. The substrate 1100 having the depressionsand the covering material 1123 having the projections are adhered toeach other so as to face each depression and each projection.

In this embodiment, the protective film 1118 and the electrode 1101 aremade of a same material through same steps. The protective films 1118and 1117 may be made of one kind or plural kinds of films selected formthin conductive films and thin insulating films. As for the thinconductive films, a film made of one or more elements selected from Al,Ti, MO, W, and Si may be used. As for the thin insulating film, a filmcomposed of one or more materials selected from silicon nitride, siliconoxide, silicon nitride oxide, aluminum nitride, aluminum oxynitride,aluminum nitride oxide, aluminum oxide, diamond like carbon (DLC), acarbon nitride (CN) film, and siloxane polymer may be used.

An interlayer film 1124 may be made of a film comprising one kind orplural kinds of materials selected from inorganic materials (such assilicon oxide, silicon nitride, silicon oxynitride, and silicon nitrideoxide) and photosensitive or nonphotosensitive organic resin materials(such as polyimide, acrylic, polyamide, polyimide amide, resist,benzocyclobutene, and siloxane polymer), or a laminated layer of theseand the like. In this embodiment, the interlayer film 1124 is made ofphotosensitive acrylic.

In this embodiment, in order to form the projections at the side of thecovering material, the insulators (also referred to as banks, partitionwalls, barriers, embankments etc.) 1120 a, 1120 b, and 1120 c and theprotective film 1117 are laminated. However the present invention is notlimited to the laminated structure. The projections may be so formed bya single layer structure or a laminated structure comprising four ormore layers, or by processing the covering material. The coveringmaterial may be processed by mechanically cutting the covering materialin accordance with the material of the covering material, or by dryetching or wet etching to form the projections. When the projections areformed by using a film at the side of the covering material, thematerial for the projections is not particularly limited, and theabove-mentioned materials used for the protective film and theinterlayer film may be used. In this embodiment, the insulators 1120 a,1120 b, and 1120 c are made of the photosensitive acrylic which is anorganic resin material, whereas the protective film 1117 is made of asilicon nitride film.

The depressions 1121 a, 1121 b, and 1121 c in the sealing region areformed so as to contact with the substrate in this embodiment.Alternatively, these depressions may be formed until they contact with adense base film. The openings may be formed in a hydrophilic film, whichserves as a path for moisture, and hence, the depth of each opening maybe set arbitrarily. Although the openings may be covered with asingle-layer protective film in this embodiment, the openings may alsobe covered with a laminated protective film in which plural films arelaminated.

Since the depressions formed over the substrate 1100 and the projectionsformed over the covering material 1123 are formed so as to match witheach other, a sealing material sandwiched therebetween is pressed,extended, and adhered to a gap between the depressions and projections.Accordingly, when minute amounts of moisture and oxygen penetratethrough the sealing material, such contaminants hardly intrude into theinterior of the display device since the contaminants have to move alonga long zigzag path due to the depressions and projections.

Meanwhile, as illustrated in FIG. 16, a portion in which the edgeportion of the insulating layer of the display device in this embodimentis exposed, is covered with the protective film 1118. In FIG. 16,reference numeral 1600 is a substrate, reference numeral 1601 is anelectrode, reference numeral 1611 is a pixel electrode, reference 1612is an insulating film, reference numeral 1613 is an EL layer referencenumeral 1614 is a cathode, reference numeral 1615 is an EL element, andreference numeral 1630 is a passivation film. In a sealing region,depressions 1621 a, 1621 b and 1621 c are formed at the side of thesubstrate 1600 by openings 1625 a, 1625 b, and 1625 c and a protectivefilm 1618 for covering the openings. At the side of the coveringmaterial 1623, projections 1622 a, 1622 b, and 1622 c are formed byinsulators 1620 a, 1620 b, and 1620 c, and another protective film 1617for covering the insulators. The substrate 1600 having the depressionsand the covering material 1623 having the projections are adhered toeach other by a sealing member 1619 so as to face each depression andeach projection. In this embodiment, a region between the openings andthe edge portion of the insulating layer is covered with the sameprotective film 1617 and 1618. However, the openings and the edgeportion of the insulating layer may be covered with different protectivefilms, respectively. According to the structure in FIG. 15, intrusion ofthe contaminants into the interior of the display device can be furtherprevented, thereby enhancing the reliability of the display device.

According to the present invention, even if moisture and oxygenpenetrate through the sealing material and the interlayer film 1124 madeof acrylic etc., which is exposed to the atmospheric air, since moistureand oxygen are shut out by the protective film, an EL element and TFTsformed inside the display device can be protected. As a result,deterioration of an EL display device due to moisture and oxygen can beprevented. When a plurality of protective films are laminated, thefunction of blocking the contaminants such as moisture can be furtherimproved, thereby obtaining a display device with higher reliability.

Although the foregoing structure of the sealing region is applied to thecase of the EL display device in this embodiment, the structure of thesealing region of the present invention can also be applied to a liquidcrystal display device. In the case of the liquid crystal displaydevice, a display device in which a display portion is formed of aliquid crystal as substitute for the EL element may be manufactured byutilizing the structure of the sealing region according to the presentinvention.

Embodiment 3

In Embodiment 3, an arrangement of wirings formed around the peripheryof a display device will be described with reference to FIG. 17. In thisembodiment, a protective film and the wirings are made of a samematerial through same steps.

In FIG. 5, in a portion 411 surrounded by a circle, the wirings for apixel portion are connected to a FPC (flexible printed circuit). Thearrangement of the wirings of the display device according to thepresent invention is depicted in FIG. 17. A first anode 2202 having anoutermost wiring connected to the FPC is arranged in the outmost edge ofthe device, whereas a cathode 2201 is arranged in the innermost edge ofthe device. Subsequently, a sealing material is formed so as to cover aconnection portion between the outermost first anode 2202 and the FPC.The periphery of the display device comprises a first region with thefirst anode formed thereon and a second region where is the connectionportion between the wirings and the FPC. In this embodiment, the secondregion resides in one side of the periphery of the display devicecomposed of four sides, whereas the first regions reside in the otherthree sides thereof.

FIG. 18 shows a cross sectional view taken along a like B-B′ of thedisplay device in FIG. 17. An electrode 62 connected to the FPC isformed on a substrate 60, and the sealing material 63 is formed thereon.A film such as an interlayer film including an organic resin materialunderneath the electrode, which is connected to the FPC, is removed byetching and the like in advance, and an insulating layer including theorganic resin material etc. is not exposed to the outer portion.Therefore, in the edges of the display device, the insulating layerincluding the organic resin material underneath the sealing material isperfectly protected from the outside air with the protective film madeof the same material as the anodes, and the scaling material. In thedisplay device according to the present invention, the peripheral edgesthereof can be completely covered with no space, thereby blockingmoisture sufficiently.

With respect to the arrangement of the wirings, an outermost wiring maybe connected to the other wiring such as the FPC at the outmost portion,and the kind, polarity, and number of the wirings may be arbitrarilyselected.

Embodiment 4

Various display devices (such as an active matrix display device, and anactive matrix EC display device) can be manufactured by applying thepresent invention. That is, the present invention can be applied tovarious electronic equipment in which such display devices areincorporated in display portions.

The following can be given as such electronic equipment a video camera;a digital camera; a projector; a head mounted display (a goggle typedisplay); a car navigation system; a car stereo; a personal computer; amobile information terminal (such as a mobile compute a cellular phone,and an electronic book); and the like. Examples of the electronicequipment are illustrated in FIGS. 12A to 12F, and 13A to 13C.

FIG. 12A is a personal computer including a main body 3001, an imageinput portion 3002, a display portion 3003, a keyboard 3004, and thelike. The personal computer of the present invention is completed byapplying the present invention to the display portion 3003.

FIG. 12B is a video camera including a main body 3101, a display portion3102, a voice input portion 3103, operation switches 3104, a battery3105, an image receiving portion 3106, and the like. The video camera ofthe present invention is completed by applying the display devicemanufactured according to the present invention to the display portion3102.

FIG. 12C is a mobile computer including a main body 3201, a camerasection 3202, an image receiving portion 3203, an operation switch 3204,a display portion 3205, and the like. The mobile computer of the presentinvention is completed by applying the display device manufacturedaccording to the present invention to the display portion 3205.

FIG. 12D is a goggle type display including a main body 3301, a displayportion 3302, an arm portion 3303, and the like. A flexible substrate isused as a substrate for the display portion 3302, and the goggle typedisplay is manufactured by making the display portion 3302 carved. Alightweight and thin goggle type display is realized. The goggle typedisplay of the present invention is completed by applying the displaydevice manufactured according to the present invention to the displayportion 3302.

FIG. 12E is a player using a recording medium recording a program(hereinafter referred to as a recording medium) which includes a mainbody 3401, a display portion 3402, a speaker portion 3403, a recordingmedium 3404, operation switches 3405, and the like. The player uses aDVD (digital versatile disc), a CD (compact disc), and the like as therecording medium, and can be used for music appreciation, filmappreciation, games, and Internet. The recording medium of the presentinvention is completed by applying the display device manufacturedaccording to the present invention to the display portion 3402.

FIG. 12F is a digital camera including a main body 3501, a displayportion 3502, a view finder 3503, operation switches 3504, an imagereceiving portion (not shown), and the like. The digital camera of thepresent invention is completed by applying the display devicemanufactured according to the present invention to the display portion3502.

FIG. 13A is a cellular phone including a main body 3901, a voice outputportion 3902, a voice input portion 3903, a display portion 3904,operation switches 3905, an antenna 3906, and the like. The cellularphone of the present invention is completed by applying the displaydevice manufactured according to the present invention to the displayportion 3904.

FIG. 13B is a portable book (electronic book) including a main body4001, display portions 4002 and 4003, a recording medium 4004, operationswitches 4005, an antenna 4006, and the like. The mobile book of thepresent invention is completed by applying the display devicemanufactured according to the present invention to the display portions4002 and 4003.

FIG. 13C is a display including a main body 4101, a supporting section4102, a display portion 4103, and the like. The display portion 4103 ismanufactured by using a flexible substrate, thereby realizing alightweight and thin display. In addition, the display portion can bemade curved. The display of the present invention is completed byapplying the display device manufactured according to the presentinvention to the display portion 4103.

As set forth above, the application range of the present invention isextremely so wide, and the present invention can be applied to theelectronic equipment in various fields.

Embodiment 5

In Embodiment 5, an example of a one-sided emission type display devicemanufactured according to Embodiment 1 will be described with referenceto FIGS. 19A and 19B.

In FIG. 19A, reference numeral 1900 denotes a substrate, referencenumeral 1950 is an interlayer insulating film, reference numeral 1952denotes an electrode, reference numeral 1953 denotes a pixel electrode,reference numeral 1913 denotes an EL layer, reference numerals 1914,1923 denote cathodes, reference numeral 1915 denotes an EL element,reference numeral 1922 denotes a passivation film, and reference numeral1921 denotes a covering material. In a sealing region, an opening 1918is formed at the side of the substrate 1900, and the opening is coveredwith the protective film 1919. The covering material 1921 and thesubstrate 1900 are bonded to each other with a scaling material 1917formed over the opening and a protective film.

A display device as illustrated in FIG. 19A is a one-sided emission typeand has a structure in which light is emitted in an upward direction asdepicted by an arrow. In this case, the pixel electrode 1953 functionsas an anode and is made of a reflective metal film. As for thereflective metal film, a metal film having higher work function such asplatinum (Pt), and gold (Au) is used for making the metal film to serveas the anode. Since such metal films having higher work function areexpensive, the pixel electrode may be formed as follows. The metal filmshaving higher work function is laminated on an inexpensive metal filmsuch as aluminum film and a tungsten film such that platinum or gold isexposed at least on a top surface. The cathode 1914 is a thin metal film(preferably with a thickness of from 10 nm and 50 nm), and is made of amaterial including an element belonging to Group 1 or 2 in the periodictable (for example, Al, Ag, Li, Ca, or an alloy of these such as MgAg,MgIn, AlLi, CaF₂, and CaN) with lower work function in order to make themetal film to function as a cathode. Further, a conductive oxide film(typically, an ITO film) that serves as the cathode 1923 is laminated onthe cathode 1914, and then the passivation film 1922 is formed thereon.

When the structure as illustrated in FIG. 19A is employed, lightgenerated from the EL element is reflected by the pixel electrode 1953,and emitted through the cathodes 1914 and 1923.

In FIG. 19B, reference numeral 1800 denotes a substrate, referencenumeral 1852 denotes an electrode, reference numeral 1853 denotes apixel electrode, reference numeral 1813 denotes an EL layer, referencenumeral 1814 denotes a cathode, reference numeral 1815 denotes an ELelement, reference numeral 1822 denotes a passivation film, andreference numeral 1821 denotes a covering material. In the sealingregion, an opening 1818 is formed at the side of the substrate 1800, andthe opening is covered with a protective film 1819. The coveringmaterial 1821 and the substrate 1800 are bonded together with a sealingmaterial 1817 provided between the opening and the protective film.

FIG. 19B also shows a display device of one-sided emission type, whichemits light in a downward direction as depicted by an arrow. In thisembodiment, a transparent conductive film is formed and etched into apredetermined shape so as to form a pixel electrode 1853, which servesas an anode. As for the transparent conductive film, a compound ofindium oxide and tin oxide, a compound of indium oxide and zinc oxide,zinc oxide, and tin oxide can be used. Preferably, the cathode 1814 ismade of a metal film (with a thickness of from 50 nm to 200 nm)comprising Al, Ag, Li, Ca, or an alloy of these such as MgAg, MgIn, andAlLi. The passivation film 1822 is formed on the cathode 1814.

In the case of using the structure as depicted in FIG. 19B, lightgenerated from the EL element passes through the pixel electrode 1853and is emitted through the substrate 1800 side.

According to the present invention, the path for moisture in the displaydevice, which is an insulating layer containing an organic resinmaterial, is shut out. Therefore, it is possible to prevent moisture andoxygen, which exist outside, of the display device from penetrating intothe display element in the interior of the display device through theinsulating film containing a hygroscopic organic material and the like.As a result, the deterioration of the display device can be prevented,thereby improving the reliability of the display device.

Embodiment 6

The reliability evaluation of a display device manufactured according tothe present invention is carried out. More specifically, it is confirmedthat the display device according to the present invention has anadvantageous effect of blocking moisture from penetrating into theinterior of the display device so as to prevent various deteriorationssuch as decrease in luminance of an EL element.

As described in Embodiment 3, the display device is manufacturing insuch a manner that wirings are formed in the periphery of a displaypanel. A sealing material is formed on the wirings to bond a TFTsubstrate and an opposing substrate. A cross sectional view of a sealingregion composed of a sealing material in the periphery of the displaypanel is illustrated in FIG. 20A, while a result of reliabilityevaluation on the display panel is illustrated in FIG. 20B.

The display panel applied with the present invention is manufactured asfollows. An insulating layer 70 is partly removed to form a depression,and then wirings and protective films 71 a and 72 a, which are made ofthe same material as a pixel electrode, are formed so as to cover thedepression through the same step. The outer edge portion of theinsulating layer 70 is also formed to cover the wirings and protectivefilms 71 b, 72 b made of the same material as the pixel electrode, and asealing material 73 is formed thereon. A TFT substrate 75 and anopposing substrate 76 are bonded to each other with the sealing material73. The wirings are made of Al, the pixel electrode is made of ITO, andthe insulating layer is made of acrylic.

The display panel manufactured as illustrated in FIG. 20A is storedunder an atmosphere with a temperature of 65° C. and a humidity of 95%for 1,000 hours, and then a voltage is applied thereto so as to make thedisplay panel to emit light FIG. 20B shows five observation photographsin which four photographs indicate corner portions and one photographshows a central portion inside of a pixel portion of the display panelmanufactured according to the present invention. The pixel portion asshown in the photographs is enlarged with a microscope, wherein aplurality of pixels emitting light respectively and constituting thepixel portion can be observed. Emission failures such as decrease inluminance and nonluminous portions are not observed in each pixel in anyportions. It is further confirmed that deterioration in the EL elementwhich contributes to light emission is not generated. As a result, thepresent invention provides an advantageous effect of blocking moistureoutside of the display device which causes deterioration of the ELelement from penetrating into the display device.

As a comparative example, another display panel is manufactured asfollows. A depression is not formed in an insulating layer 80, wiringsand wirings 81 a, 81 b, 82 a, and 82 b made of a pixel electrode areformed over the insulating layer 80, and then a TFT substrate 85 and anopposing substrate 86 are adhered to each other with a sealing material83 formed over the wirings. A cross sectional view of the display deviceof the comparative example is illustrated in FIG. 21A, while the resultof the reliability evaluation of the display panel is shown in FIG. 21B.In FIG. 21A, the insulating layer 80 is exposed to the outside air.

The display panel manufactured as depicted in FIG. 21A is stored underan atmosphere with a temperature of 65° C. and a humidity of 95% for 190hours, and then a voltage is applied thereto so as to make the displaypanel to emit light FIG. 21B shows nine observation photographs in whicheight photographs indicate peripheral edge portions and one photographindicates a central portion inside a pixel portion of the display panelof the comparative example. The pixel portion shown in the photographsis enlarged with a microscope, and a plurality of pixels emitting lightindividually and constituting the pixel portion can be observed in thephotograph. In each pixel in the peripheral portions, however,nonluminous portions or portions in which luminance is degraded aregenerated from four corners of the panel nearly to pixels in the thirdrows and seventh columns even though the display panel is stored onlyfor 190 hours. This is attributed to the fact that light-emittingmaterials constituting the EL element and the like are deteriorated bythe penetration of moisture through the insulating layer 80 from theperipheral portions.

As set forth above, it is confirmed that a display panel with higherreliability in which decrease in luminance of the EL element isprevented can be manufactured according to the present invention.

What is claimed is:
 1. A display device comprising: a substrate; a thinfilm transistor formed over the substrate; a interlayer insulating filmformed over the thin film transistor, an opening formed in theinterlayer insulating film; a protective film formed on the opening; asecond substrate provided over the interlayer insulating film; and asealing material for adhering the first and second substrates, formedover the interlayer insulating film, wherein the opening is formed at aperiphery of the substrate.